Well think of it this way, someone who has been constantly friendly and is one of your best mates in life has been wanting to play in your game, they don't get picked randomly so you slot them in. This may be unfair but then it is also how it works in the online games here. The more you put in the forum, like the moderators, the more you get out. So the mods do so much here so as a small reward if they want to play they will get to. However newer members are still picked, I didnt get picked at first but still watched and now I think myself as an experienced player. However I still didn't get into the asylum. Just take it on the chin and say to yourself "next time".
Also if you really want to improve your chances, keep watching the game and comment on it in the discussion threads, make it known to people that you are ready and Im sure you will be picked.